Basically, you're purchasing the ballast and hood. Cords and socket prices are minimal.
"Used" bulbs will need replacements. "I" recommend an electrical supply outlet. "Hydro" stores inflate the prices. Commonly $100-$200+ at the plant stores, but the supply house gets you out the door for under $75.
"An older model"....?? hmmmmmmmmm
I got my first light as a used unit, ($50) and it was old. It ran fine for about 3 yrs before the ballast took a crap on me.